Photoisomerization of Bicyclo[3.1.1]heptan-2-ones in Methanol: Chemical Transformations of 'Verbanones'

Abstract

ALEX G. FALLIS. Can. J. Chern. 53, 1657 (1975. The products (predominantly unsaturated aldehydes) from photolysis in methanol of a series of 6,6-dirnethylbicyclo[3.1 .l]heptan-2-ones are reported. These results are rationalized on the basis of stereochernical interactions and the apparent preference for cleavage to occur adjacent to the less highly substituted a-carbon but more stable alkyl radical. It is concluded that the photochemical behavior of a-cyclobutyl ketones displays a closer parallel to the a-cyclopropyl ketones than previously recognized and that cleavage will occur preferentially on the side of the carbonyl group remote from the four-membered ring whenever possible. The synthetic steps involved in the preparation of the ketones from 'pinene' precursors are described.ALEX G. FALLIS. Can. J. Chem. 53, 1657Chem. 53, (1975. On rapporte les produits (principalement des aldkhydes non-saturks) formis lors de la photolyse dans le methanol d'une sQie de dimkthyl-6,6 bicyclo[3.1.1]heptanones-2. On rationalise les resultats en se basant sur les interactions sterkochimiques et la prkfkrence apparente pour que la coupure se produise dans la position adjacente a celle du carbone a moins substitue rnais posskdant le radical alkyle le plus stable. On en conclut que le comportement photochimique des a-cyclobutyl dtones montre un parallklisrne plus pres de celui des a-cyclopropyl cetones qu'il n'avait kte reconnu auparavant; de plus, chaque fois que cette coupure sera possible, la coupure se produira prkferentiellement sur le c6tk du groupement carbonyle Cloignk du cycle a quatre rnernbres. On dkrit les ktapes synthktiques irnpliqukes dans la prkparation des cktones a partir de prkurseur du type 'pinhe'.[Traduit par le journal]

ChemInform Abstract: PHOTOCHEMISTRY OF TRICYCLO(3.3.1.02,7)NONAN‐6‐ONES

“…These were shown to be 2-oxatetracyclo[4.2.2.0~~9.0~~~] decanes on the basis of the spectroscopic data summarized in the Table. Their formation from 2 can readily be explained by preferential u-cleavage on the side of the carbonyl group remote from the four-membered ring [5] and abstraction of the more easily accessible hydrogen atom on C(4) to yield the intermediate aldehyde 4 which then photocyclizes to 3 (Scheme 2). These were shown to be 2-oxatetracyclo[4.2.2.0~~9.0~~~] decanes on the basis of the spectroscopic data summarized in the Table. Their formation from 2 can readily be explained by preferential u-cleavage on the side of the carbonyl group remote from the four-membered ring [5] and abstraction of the more easily accessible hydrogen atom on C(4) to yield the intermediate aldehyde 4 which then photocyclizes to 3 (Scheme 2).…”

“…These were shown to be 2-oxatetracyclo[4.2.2.0~~9.0~~~] decanes on the basis of the spectroscopic data summarized in the Table. Their formation from 2 can readily be explained by preferential u-cleavage on the side of the carbonyl group remote from the four-membered ring [5] and abstraction of the more easily accessible hydrogen atom on C(4) to yield the intermediate aldehyde 4 which then photocyclizes to 3 (Scheme 2). The irradiation of 2c under similar conditions yields equal amounts of 3c and the cyclopentadiene derivative 5.…”

Photochemistry of Tricyclo[3.3.1.02,7]nonan‐6‐ones. Preliminary communication

“…We now discuss results on the photochemistry of the tricyclo[3.3.1.02~7]nonan-6-ones 2. to the formation of 3a and 3b. These were shown to be 2-oxatetracyclo[4.2.2.0~~9.0~~~] decanes on the basis of the spectroscopic data summarized in the Table. Their formation from 2 can readily be explained by preferential u-cleavage on the side of the carbonyl group remote from the four-membered ring [5] and abstraction of the more easily accessible hydrogen atom on C(4) to yield the intermediate aldehyde 4 which then photocyclizes to 3 (Scheme 2). Such oxetane formations have also been observed in direct irradiations of bicyclic ketones [l] [3].…”